The wireless communications technologies have been widely used in various fields and have advantages such as low costs, high flexibility, and convenience for device maintenance. Because free space is used to propagate information-carried carriers in wireless communication, communication information of two parties may be exposed easily, and is open to an eavesdropper. Therefore, a wireless communications security problem needs to be resolved at a physical layer.
In the wireless communications technologies, a precoding technology is an important means to improve wireless communications reliability, and is one of key technologies for improving communications performance in a multiple input multiple output (MIMO) system. The precoding technology is a transmitter preprocesses a transmit signal using channel information, so as to adapt to a channel environment change and weaken multipath fading channel interference, thereby reducing a system bit error rate and improving a system throughput.
An existing method for transmitting data based on a MIMO physical layer security technology depends much on a channel. Therefore, a quicker change of a channel feature results in lower system security.